A core network is an important part of an evolved packet system (EPS). Key logical network elements of a core network may include a mobility management entity (MME), a serving gateway (S-GW), a packet data network gateway (P-GW), a home subscriber server (HSS), and the like. The P-GW is a gateway connected to an external data network, and is a user plane anchor between an access network and a non-access network. To be specific, user equipment may establish a packet data network (PDN) connection by using the P-GW, to access the external data network. When the user equipment moves, an IP address and uplink and downlink paths of the user equipment need to be anchored at a forwarding plane device such as the P-GW, to ensure service continuity when a user moves.
However, it is found in practice that when user equipment moves, service packet transmission paths of the user equipment need to be anchored at a source forwarding plane network element, leading to long uplink and downlink paths and a relatively long network latency. As communications technologies develop, broadband access technologies for user equipment, such as wireless-fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMAX), and a third-generation or fourth-generation mobile communications technology 3G/4G, have made significant progress. In addition, an EPS system also supports a plurality of PDN connections between user equipment and a PDN network, allowing the user equipment to have a plurality of PDN connections to a target node at the same time. However, for user equipment having a plurality of PDN connections, how to select a proper PDN connection from the plurality of PDN connections to improve service packet transmission quality is a problem that urgently needs to be resolved.